JSFiddle - React, Tailwind, and code Playground

HTML

<div class="topic-meta-data">
  <div class="names trigger-user-card">
    <span class="first username staff admin">
      <a href="/u/Cos" data-user-card="Cos">Cos</a>
    </span>
  </div>
</div>

CSS

.names span.admin a::after {
    content: "";
    width: 17px;
    height: 14px;
    margin-left: 5px;
    background-image: url(https://www.dropbox.com/s/0oi0y3ex3rtfvk5/cd-crown.svg?raw=1);
    background-repeat: none;
    display: inline-block;
    position: relative;
}
.names span.admin a.mystyle {
    color: red;
}

JavaScript

var cdcrowntitle = document.querySelector(".names .admin a");
cdcrowntitle.setAttribute("title", "Community Admin");
cdcrowntitle.classList.add("mystyle");